Now just here me out: What if the girls' bathroom is full up on people, or broken down for some reason. Wouldn't it be nice if a girl had to go into the boys' bathroom in an emergency, that they would have access to those things.
Boys don't have special requirements to use the bathroom. I can go anywhere just about. I can take leak on the side of the road with only a car door for privacy in ten seconds. Boom, I'm done.